3 Answers
3

The 'D Dsus2 D' part is probably just after the word 'increase' but the line was too long for one of the protocols the file has traversed, and so it got wrapped to a new line.

Some common line-length limits for text data are 72, 80, 99 (common in "beginner" software because it's so easy to type buf[99] and move on to "fun" stuff).

This should also be easy to spot because D Dsus2 D is one of several common folk-guitar ornaments (others are D Dsus4 D, A Asus4 A, Am Asus2 Am, C Cadd9 C, C Cmaj7 C) which involve a single finger-change. So in a sense it belongs at the end of a line just after the lyric. That's the moment when the singing stops and the guitar naturally needs to doing something interesting. A "sus4" or "sus2" ornament adds that little bit of interest. Other options are: descending bass-line, jump to chromatic mediant, play the changes totally straight to add suspense, slide up to a different phrasing of the same chord, do a little solo...

Just as a reference, there is something called poly chords which in concept are "stacked chords".

An example would be D above C, which is written as (but should be tighter layout wise):

D
-
C

and simply refers to a C triad chord (in any inversion) with a D triad chord (in any inversion) stacked on top of it.

One might wonder what the difference of the example is from a C6/9#11 chord? Well, not much really, but in the 'D above C' case you could expect to hear the tones of the D chord as a distinguishable unit of its own and played above the tones of the C chord. A typical presentation of this could be a jazz big band where the trombones and saxophones play a C chord but the trumpets play a D chord creating a cool tension that wouldn't have been the same with a more traditional voicing of a C6/9#11 chord. Hosting the D chord in an instrument section of its own enhances the effect. If the trumpets where to also use, say, a harmon mute it would be even clearer that they were doing something different than the tromones, further establishing the 'D above C' case.